Since their inception portable electronic devices like cell phones have used AC/DC adapters to charge their batteries from household AC power. USB connections are also used to charge portable devices using a DC current of approximately 5V, as well the USB can be used to exchange data between the USB source and the portable device.
U.S. Pat. No. 7,688,026 discloses a mobile charging adapter The charger uses a first input conversion to the battery voltage (perhaps on the order of 4.2V) and then in outputting, converts again from the battery voltage of 4.2 to the output voltage of 5V, reducing efficiency by the two conversions of one power. The input power cannot be output directly without conversion to the nature of the circuit, where the battery is connected directly to the input/output circuit, necessitating the multiple conversions outlined above, and thereby increasing complexity and reducing efficiency. Further, the charger will not work if the battery is damaged or near the end of its life.
Therefore there is a need in the art for a battery-powered charger which can output the input power directly, without the inefficiency of the battery connected between the input and the output.